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Tay-Sachs disease is a rare genetic disorder passed from parent to child. It's caused by the absence of an enzyme that helps break down fatty substances. These fatty substances, called gangliosides, build up to toxic levels in the brain and spinal cord and affect the function of the nerve cells. changes in the gene on chromosome 15 are from a point mutation. this results in a frameshift effect that makes the protein non-functional, a build-up in these non-functional proteins in the brain cell lead to neurological degeneration, generalised paralysis and death at about 4 years old.

Symptoms

Exaggerated startle response when the baby hears loud noises.

Cherry-red spots in the eyes.

Loss of motor skills, including turning over, crawling and sitting up.

Muscle weakness, progressing to paralysis.

Movement problems.

Seizures.

Vision loss and blindness.

Hearing loss and deafness

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-Rare genetic disorder also known a 5p syndrome.
-Mutation which causes this is deletion 10-20% deleted from end of the short arm of chromosome 5.
-Deletion most often occurs as random event during formation of eggs or sperm.
-Cry of affected child is high pitched that sounds like a cat.
-Problem with nervous system and larynx.
-Heart defects.
-Severe speech and cognitive delays.
-Behavioural problems.
-Small head.
-eyes spaced far apart.
-Narrow and high palate.
-Usually die in childhood.

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Duchenne Muscular Dystrophy (DMD) Claire Ballantyne

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Duchenne Muscular Dystrophy (DMD) Claire Ballantyne

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Duchenne Muscular Dystrophy (DMD) is a genetic muscle-wasting disease. DMD occurs when a gene fails to code for the protein dystrophin. Dystrophin is essential to the development and function of muscles including skeletal and cardiac muscles as it is part of the group of proteins that strengthen and protect muscles during relaxation and contraction.

DMD is caused by either a deletion or nonsense mutation in a particular gene found on the X chromosome, this is X-linked recessive inheritance. In most cases of DMD, the condition is genetically passed from carrier mothers to their sons but can also be caused by a random mutation of genes as the child develops.

As children with DMD usually develop normally in early childhood, symptoms usually start between ages 2 and 5, beginning with signs of clumsiness including frequently falling and having trouble walking. Over time the muscle weakness will progress and walking, moving, sitting and lifting will progressively become harder, and as they become a teenager they will usually be full-time wheelchair users.

https://www.parentprojectmd.org/about-duchenne/what-is-duchenne/genetic-causes/

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Beta Thalassemia is an inherited blood disorder characterised by reduced levels of functional haemoglobin.

Haemoglobin is found in red blood cells; it is the red, iron-rich, oxygen-carrying pigment of the blood. The main function of red blood cells is to deliver oxygen throughout the body.

Beta Thalassemia has three main forms – minor, intermedia and major, which indicate the severity of the disease. Individuals with Beta Thalassemia minor usually don't have any symptoms (asymptomatic) and individuals often are unaware that they have the condition. Some individuals do experience very mild anaemia. Individuals with Beta Thalassemia major have a severe expression of the disorder; they often require regular blood transfusions and lifelong, ongoing medical care.

The symptoms of Beta Thalassemia intermedia are variable and severity falls in the broad range between the two extremes of the major and minor forms. The characteristic finding of Beta Thalassemia is anaemia, which is caused because red blood cells are abnormally small (microcytic), are not produced at the normal amounts, and don't contain enough functional haemoglobin. Consequently, affected individuals don't receive enough oxygen-rich blood (microcytic anaemia) throughout the body. Affected individuals may experience classic signs of anaemia including fatigue, weakness, shortness of breath, dizziness or headaches. Severe anaemia can cause serious, even life-threatening complications if left untreated.

Affected individuals are treated by regular blood transfusions. Because of repeated blood transfusions individuals with Beta Thalassemia major and intermedia may develop excess levels of iron in the body (iron overload). Iron overload can cause a variety of symptoms affecting multiple systems of the body, but can be treated with medications.

Mutation

Beta Thalassemia is caused by mutations in the haemoglobin beta (HBB) gene. Individuals with Beta Thalassemia minor have a mutation in one HBB gene, while individuals with the intermediate and major forms have mutations in both HBB genes.

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Sickle Cell:

It is an inherited disorder, where one of the genes on chromosome 11 codes for haemoglobin undergoes substitution where it becomes expressed as an unusual form of haemoglobin, called haemoglobin S. This is missense, where one small altercation can lead to profound changes in the folding and ultimate shape of the haemoglobin S molecule that makes it an inefficient carrier of oxygen.

People who are homozygous for the mutated allele experience drastic consequences.

Red blood cells are normally round and flexible, people with sickle cell have a change or mutation in the gene.

This faulty gene causes haemoglobin to form strands in the red blood cells making them less flexible with a crescent or a sickle shape. A sickle is a tool used to cut long grass.

This can cause blockages in blood vessels and interfere with blood circulation.

When cells cannot pass through blockages to reach tissue and organs, meaning they don’t get oxygen for respiration. This causes pain causing sickle cell crisis and in some cases death.

People who are heterozygous for the mutant allele do not have sickle cell anaemia and instead have a milder condition called sickle cell trait. The haemoglobin cell does not show sickling so the slight anaemia that they have tends to be less moderate.

4.4 million people have it, 43 million are carriers.

80% live in central Africa

They are also affected by the disease malaria

Having the sickle cell allele protects you from malaria, meaning you are more likely to survive and pass on the gene

This means the number of people suffering from sickle cell is higher in malaria regions

Malaria is caught from mosquitos that spend part of their life cycle inside red blood cells. When the parasites entre the cells of carriers, the cells burst before the parasite can develop, killing the parasite and ending their life cycle.

Symptoms:

Anaemia – the sickle cells break apart easily and die, leaving you with fewer red blood cells

Episodes of pain

Swelling of hands and feet

Frequent infections

Delayed puberty or growth

Visual problems

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DMD is a muscle wasting condition due to a lack of protein called Dystrophin. This causes the muscle fibres to break down and replace them with fibrous and fatty tissue, causing the muscles to weaken.

Duchenne Muscular Dystrophy is caused by a mutation in the genetic code on a gene called Dystrophin located on the X chromosome caused by a nonsense mutation.

Just over 50% of cases of the condition is inherited by the mother who was a carrier. Although the mutation can also be de novo.

Women are rarely affected by DMD due to them having a second X chromosome where the dystrophin protein will be produced, which makes these women carriers. It is possible for carriers to have a degree of muscle weakness this is known as “manifesting carriers”.

A carrier’s son has 50:50 chance of being affected by DMD

A carrier’s daughter has a 50:50 chance of being a carrier.

Duchenne muscular dystrophy (DMD) - Overview | Muscular Dystrophy UK

Emma Heenan